Phylum: Charophyta   Family: Desmidiaceae

Staurodesmus pterosporus  (P. Lundell) Bourrelly

An acidophile of little known distribution. Current finds have been in moorland pools and bogs

References: 
Coesel, P.F.M. & Meesters, K.J. (2013) European Flora of the Desmid Genera Staurastrum and Staurodesmus
West, W., West, G.S. & Carter, N. (1923) A Monograph of the British Desmidiaceae, Volume 5